Method of treating steel



Patented Nov. 7 25, 1941 2,263,906 METHOD OF TREATING sTEEL Stanley B. Sovatkin, Brooklyn, N. Y.

No Drawing.

Application May 15, 1940,

Serial No. 335,326

7 Claims.

This invention relates to the art of heat treat; ing and welding steel and to steel treating compositions for use therein.

Heretofore the common run of tonnage or S. A, E. steels has not been used for purposes for which tool steel is intended. Further, it is recognized that in the absence of special ingredients, e. g. chromium and manganese or nickel, ordinary steels do not possess any appreciable corrosion resistant quality.

I have found that by heat treating steel, especially steels of the S. A. E. variety, with certain substances hereinafter mentioned, there may be obtained unusual and highly advantageous results. Thus, steels of relatively low carbon content, when treated in accordance with the invention, develop qualities of resistance to abrasion and shock and longevity which are appreciably greater than those obtainable when similar steels are treated in conventional manner, and which renders such low carbon steels suitable for many uses for which higher grades of steel, such as tool steel, were aloneconsidered suitable heretofcre. invention, moreover, does not cause the relatively high degree of brittleness which, heretofore, has been regarded as a concomitant of hardness in steels.

Furthermore, steels treated in accordance with my invention ar characterized by a corrosionresistant or stainless quality which enables them to resist oxidation and attack by weak acids, al-- though steels of comparable initial character, not treated in accordance with my invention, possess virtually no corrosion-resistant or stainless qualities.

Again, when steel which is to be cold worked by swaging is treated in accordance with the invention, its surface condition is improved in a manner which renders the steel better suited for cold working operations.

Furthermore, the use of certain substances which are involved in the invention in-connection with the welding of steel brings about advantages more fully explained hereinafter.

The substances to which I hav referred, and

which, because of their unique and beneficial effects on steel subjected to the action thereof, I prefer to term energizers, are ammonium chloride and manganous chloride. Preferably, these substances which are employed together are used in comminuted form and in admixture with one or more other materials, e. g, those of the type known as carburizing materials, such The treatment in accordance with my ,of the invention.

used in comminuted form. The ammonium chlo-.

ride and manganous chloride may, for example, be mixed with one or more of the following: Petroleum coke, charcoal, barium carbonate, calcium carbonate, sodium carbonate, sodium bicarbonate, sodium chloride, potassium cyanide, potassium ferrocyanide, potassium bichromate, potassium dichromatef The ammonium chloride and manganous chloride are each present, in any mixture thereof with other material or materials, to the extent of from about 1 /r-% to about 24%, by weight, of the total mixture.

Although I do not fully understand why these energizers should bring about the unusual and advantageous results for which they have, in fact, been found to be responsible, I believe that subjecting steel, at a temperature above its upper critical temperature, to the action of ammonium chloride and manganous chloride in the presence of the other substances referred to produces a molecular change in, and improves the normally imperfect microstructure of, the steel, particularly at the surface thereof, and that such change and improvement are, at least in part, responsi ble for the unusual results flowing from exercise It is also possible that the "results are due in whole or in part to the entry of manganese and/or nitrogen into the constitution of the steel as a result of the process.

I have found that the following mixtures, including the ammonium chloride and manganous chloride to which I have referred, have been productive of particularly good results:

Compound A Compound B Percent Percent by Ingredient y Ingredient weight weight 1Q Potassium lerrocy v 34. 24 Sodium chloride. snide. 35 Sodium carbonate.

11 Sodium chloride. 18.82 Potassium lerrocy- 9 Bicarbonate of soda. anide. 2% Potassium dichrom- 2. 04 Ammonium chloride. ate. 2. 04 Manganous chloride. 6 Barium carbonate. .56 Potassium ferryocy- 50 Charcoal. an e.

6 Ammonium chloride. 62 Sodium chloride. 5% Manganous chloride. 51 Sodium bicarbonate.

- 34 Barium carbonate. 4. 83 Charcoal. 1 Potassium dichrom- It may be said, therefore, that the. presentinvention, in one aspect, resides in the provision of an energizer blend comprising ammonium other material or materials also preferably being 55 chloride and manganous chloride. In another aspect, it ma be said that the present invention includesv heating steel above itsupper critical temperature in the presence of, or while the steel is subjected to the action of, manganous chloride and ammonium chloride. In still other aspects, it may be said that the invention contemplates the use of these energizers in connection with the annealing of high carbon steel, and in connection with the welding of steel, as more fully explained hereinbelow.

As illustrative of the eflicacy of the present invention in processing steel of relatively low initial carbon content (i. e., of the order of .5% or less) and of imparting desirable surface characteristics thereto, I cit the following instances:

1. An S. A. E. 3135 steel was heated in compound A at a temperature of 1750 F. for 35 minutes and was then quench'edin oil. The steel was found to have developed a surface hardness of 50-55 Rockwell scale, and the surface of the steel was found to be clean, and free from any deposit. (Since the various S. A. E. designations herein employed are generally understood by those skilled in the art to relate, respectively, to steels of various particular compositions. no further designation or description of the steels so referred to herein are deemed necessary.)

2. An S. A. E. 3115 steel was heated in compound A for 3 hours at 2000 F. and was then quenched in brine. The steel was found to have developed a surface hardness of 63-66 Rockwell C scale, and the depth of penetration of the hard case thus formed was sixty thousandths (.060) of an inch.

3. An S. A. E. 4615 steel was heated in compound B at 1650 F. for 2 hours and was then quenched in oil. The steel was found to have developed a surface hardness of 60-63 Rockwell 0 scale, and the depth of penetration of the hard case thus formed was one hundred and twenty thousandths (.120) of an inch.

'4. An S. A. E. 4615 steel was heated in compound B for 1 hour at 1600 F. and was then quenched in brine. The steel was found to have developed a surface hardness of 58-60 Rockwell C scale, and the depth of penetration of the hard case thus formed was twenty thousandths (.020) of an inch.

It will thus be noted that through practice of the invention, each of these steels of relatively low carbon content attained a degree of hardness and a depth of penetration which it would not, and could not, have attained if such steel were treated in conventional manner.

As indicative of the manner in which the present invention enables low carbon steels of the tonnage variety to replace high carbon tool steels outlasted, by an average of about 60,000 feet of tubing, similar mandrels, made of high carbon tool steel and conventionally treated, subjected to identical usage. The procedure followed in treating the former mandrels was to heat them in compound A at 1800 F. for about 2 to 3 hours and then to quench them in oil; they were then reheated in compound B at about 1500 F, for minutes, and quenched in brine, after which they were tempered or drawn in the customary manner.

3. Blanking dies made of S. A. E. 1045 steel treated in accordance with the invention, successfully blanked as many pieces of stainless steel as dies made of a well known tool steel of high grade. The procedure followed in treating the S. A. E. 1045 steel was to heat it in compound A for 2% hours at 1700 F. and then to quench it in in many industrial applications, I cite the following instances of actual experience in the use of the invention:

1. Thread rolling'dies made of S. A. E. 1045 steel treated in accordance with the invention have been used for threading more than one million screws without showing any signs of deterioration or fracture. The procedure followed in treating the die parts was to heat them in compound A for 2 hours at 1800 F. and then to quench them in oil; they were then reheated in compound B for approximately 15 to 20 minutes at a temperature of about 1500' F., and quenched 'in brine, after which they ,.were tempered or drawn in the customary manner.

. 2. Expanding mandrels, made of S. A'. E. 3135 steel treated in accordance with the invention, used in the manufacture of brass tubing, have oil; the steel was then reheated in compound B for 20' minutes at 1500 F., quenched in brine, and then tempered or drawn in the customary manner.

In one test, a brass blanking die at least forty years old, and of undetermined composition but incapable of blanking any type of steel, was heated in compound A for 2 hours at 1750 F., quenched in oil, reheated for 25 minutes in compound B at about 1500 F. and then quenched in brine. This die, after such treatment. successfully blanked a substantial quantity of stainless steel.

Other low carbon steels which were treated in accordance with the invention and which were, thereafter, found to possess characteristics generally regarded as restricted to high carbon tool steels, were the following: S. A. E. steels Nos. 1010, 1020, 1045, 2335, 3135, 6145.

As illustrative of the manner in which exercise of the invention imparts a corrosion resistant quality to steels which ordinarily would possess no such quality, I cite the following instances, representing my actual experience in the use of the invention:

1. An S. A. E. 1335 steel was heated in compound A at 1800 F. for 1 hour and was then quenched in brine. The steel thus treated successfully resisted the well known cold copper sulphate test and showed no signs of plating. After 11 days in Ringers solution, the steel showed no signs of corrosion.

2. An S. A. E. 1045 steel was heated in compound A for 1 hour, at 1750 F., quenched in brine. and then reheated in compound B at 1500 F. for 20 minutes. After 15 days in Ringer's solution, the steel showed no signs of corrosion.

As illustrative of the application of the invention to the treatment of steel having a relatively high carbon content, and intended to be cold .worked by swaging, I cite the following:

was annealed in conventional manner, 1. e., merely by having been heated to a temperature of about 1600 F. and then cooled slowly, the second step left, at the point, flash metal" or a burr formation, which had to be removed, in a separate operation, in order that the article might present a finished appearance. However, when 'liquid preparations used or adapted to be the steel was annealed by having been subjectedto the action of the energizers in association with the other materials to which I have referred, the second step was accomplished without the formation of a flash or burr. This application of the invention made it possible to produce satisfactory articles without any necessity forlremoving flash metal, and hence at an appreciable saving in both time and labor, as compared with conventional practice. The annealing procedure employed to accomplish this result was as follows: The steel to be treated was heated with compound A, at 1450" F., (a temperature above the upper critical temperature) for 1,-2 hours, in a sheet steel box, and then allowed to cool therein ata rate which metallurgists term moderately slow, to a temperature of about 500 F. The steel was then taken from the box and the remainder of the cooling was accomplished in the air,

I have further found that the use of ammonium chloride and manganous chloride, in connection with the arc welding of steel, results in the creation of a more stable arc, and less spattering of deposited metal and, in less contamination of the weld by foreign matter.

While the reasons underlying causes of such advantages afforded by the invention remain obscure, my tests have conclusively indicated that use of the invention does, in fact, afiord these benefits. Moreover, my experiments have shown that welded connections made in accordance with the invention are stronger than otherwise similar welded connections not made in accordance with the invention, thus indicating that use of the invention will, in many instances, afford substantial economies by permitting butt welds to be used where conventional practice would dictate the use the compounds A and B hereinabove referred to.

While the energizers, which together serve as and constitute a welding flux, are preferably utilized in the manner just indicated, the invention is not so limited, and contemplates the use of such energizers in any manner in which fluxes are conventionally employed.

Although, it is preferred, in most cases, to subject the steel to the action of compound A during a first heating stage and to the action of compound B during a second heating stage, it is to be understood that I may use either compound in both heating stages, and that I may subject the steel to the action of compound B during the first heating stage and to the action of compound A during the second heating stage. It has been my observation that compound A tends to bring about a depth of penetration which is greater than that afforded by compound B, and that compound B tends to. bring about a degree of hardness which is greater than that afforded by compound A. It is this observation which is the basis for the preference which I have expressed above, for it seems to me desirable, in most cases, first to obtain a relatively high degree of penetration and then to obtain a relatively high degree of hardness at the surface of the steel.

Since I recognize that those skilled in the art may make various changes in practicing the invention without departing from the scope thereof, it is intended that the foregoing description be regarded as illustrative only, and not in a limiting sense.

I claim:

1. The improvement in the art of heat-treating steel which consists in heating the steel to a temperature above its upper critical temperature in the presence of a treating compound including at least one carburizing material from about 1 /g to about 24% of ammonium chloride and While compounds substantially similar to those designated above as compound A and compound B, respectively, are preferred for use in practicing the invention in its various aspects, I wish it to be understood that my invention is not limited to compounds of the named ingredients; my energizers may be used to advantage with, for example, any and all substances understood to be embraced within the generic designation carburizing materials. Nor is the invention limited to the above specified proportions of any of the various ingredients indicated as being mixed with the energizers. The ammonium chloride and manganous chloride may be used in proportions otherthan those specified in the formulae of compound 'A and compound B; each such energizeig may be used, in mixture with other material onmaterials, in'a proportion of from about 1 /g% to about 24%. Further, it is to be understood that the energizers may be used not only in solid form, but also in cyanide baths or other used in the treatment of steel.

from about 1 to about 24% of manganous chloride.

2. The improvement in the art of heat-treating steel which consists in heating the steel to a temperature above its upper critical temperature while subjecting the steel to the action of a treating compound including at least one carburizing material, from about 5% to about 7% of ammonium chloride, and from about 5% to about 7% of manganous chloride.

3. The improvement in the art of heat-treating steel having an initial carbon content not exceeding .5% which consists in heating the steel to a temperature above its upper critical temperature while subjecting the steel to the action of a carburizing material, ammonium chloride and manganous chloride, the ammonium chlorideand-manganous chloride being each present to the extent of from 1 to about 24%, by weight, of the total treating compound.

4. In the art of heat-treating steel, heating the steel to a temperature above its upper critical temperature while subjecting the steel to the action of a treating compound including a carburizing material, from about 1 to about 24% of manganous chloride and from about 1 to about-24% of ammonium chloride, and thereafter cooling the steel'relatively slowly.

5. A relatively hard, tough, and corrosion-resistant steel having a surface condition such as results from the heating of such steel to a temperature above its upper critical temperature in the presence of a'treating compound including the presence of a treating compound including at least one carburlzing material, from about 2% to about 7% of ammonium chloride and from about 2% to about 7% of manganous chloride.

'7. A steel having a carbon content in excess of .5% and having properties rendering it particularly suitable for cold working by swaging said steel having a surface condition such as results from subjecting such steel to a temperature above its upper critical temperature in the presence of a treating compound including a carburizing material from about ,1 /i% to about 24% of ammonium chloride and from about 155% to about 24% of manganous chloride and thereafter cooling the steel relatively slowly.

STANLEY B. SOVATKIN. 

